Method for Making Ophthalmic Devices Using Single Mold Stereolithography

ABSTRACT

A method for manufacturing an ophthalmic lens comprising introducing a volume of photocurable lens material into a container, wherein said container comprises a mold surface. The method further comprises creating a digital 3-D mathematical model defining corrective needs of an eye and projecting programmed patterns of UV light through said mold via a pattern generator, wherein said programmed patterns of UV light cure said photocurable lens material into a lens shape defined by said mold surface and said digital model.

This application claims the benefit under 35 U.S.C. §119 (e) of U.S.provisional application Ser. No. 61/041,623 filed Apr. 2, 2008, hereinincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention is related to a method for making an ophthalmicdevice. In particular, the present invention is related to a method forproduction of an ophthalmic device by means of stereolithography. Inaddition, the present invention provides systems and methods for makinga contact lens for a specific patient based on the prescription.

BACKGROUND OF THE INVENTION

It is well known that contact lenses can be used for cosmetics and thecorrection of visual acuity. The ideal contact lens is one which is notonly comfortable to wear for extended periods of time, but also easilymanufactured at minimum cost. Contact lenses are described by the shapesof their back (against the eye) surface and front surface. The backsurface is shaped to fit the wearer's cornea. Typically, a contact lensmanufacturer uses only three to five different shapes for the majorityof customers. The front surface of the lens controls the visioncorrection capability of the lens. The lens' thickness is varied inorder to control its corrective properties.

Currently, a casting molding process is one of the most cost-effectivemanufacturing processes for production of contact lenses. In a typicalmolding process, a predetermined amount of a polymerizable orcrosslinkable material is dispensed in the female mold half of a moldand the mold is closed by placing the male mold half proximately to thefemale mold half to create a cavity having a desired geometry for acontact lens. Normally, a surplus of polymerizable or crosslinkablematerial is used so that when the male and female halves of the mold areclosed, the excess amount of the material is expelled out into anoverflow area adjacent to the mold cavity. The polymerizable orcrosslinkable material remaining within the mold is polymerized orcross-linked with the delivery of radiation thereto through UV light,heat action, or other non-thermal methods. Since the geometry of theophthalmic lens is specifically defined by the cavity between the maleand female mold halves and since the geometry of the edge of theophthalmic lens is defined by the contour of the two mold halves in thearea where they make contact, a contact lens is manufactured into afinal form between typically male and female mold halves, with noadditional finishing work on the surface of the lens or the edges of thelens. Such full-mold process can reduce cost in the production ofcontact lenses.

However, the manufacturing processes of corrective lenses utilize molds(soft contacts) or machining (hard contacts, intraocular lenses) thatare difficult or impossible to change in response to an individual'svision correction needs. In a typical molding process, a contact lens,which is removed from the mold after curing, needs to undergo the othermanufacturing processes such as hydration/extraction and sterilization,which can increase manufacturing cost of contact lenses. By using aprepolymer which is a water-soluble photo-crosslinkable polyvinylalcohol, a finished lens of optical quality can be produced in a moldwithin a few seconds without the necessity for subsequent extraction orfinishing steps to the contact lens. With such manufacturing process,contact lenses can be manufactured at a reduced cost and thus it ispossible to produce disposable contact lenses that are discarded by theuser after a single use.

Although some contact lens-molding processes are able to reducemanufacturing cost of contact lenses to some extent, cost associatedwith molds and production thereof can be relatively high. Partly becauseof the relatively-high cost associated with use of molds and partlybecause of difficulty in managing an inventory with a huge number ofSKUs, a family of contact lenses made by a lens molding processgenerally can only have a limited number of variations in optical powerand/or choices of base curve and/or the like. In most cases, a patienthas to use contact lenses which would have the closest match to his(her) prescription or use customized contact lenses which areexpensively produced, for example by lathing.

Moreover, in a typical molding process, the dispensing of apredetermined amount of a polymerizable or crosslinkable material intoone of the two mold halves could be a challenging manufacturing issue.For example, the viscosity of the polymerizable or crosslinkablematerial has to be within a certain specific value so that it would bepossible to dispense the polymerizable or crosslinkable material at areasonable cost. Also, one has to take all possible measures toeliminate the formation of bubbles during dispensing of thepolymerizable or crosslinkable material. All the above-statedmanufacturing issues and others related to dispensing of thepolymerizable or crosslinkable material can increase the cost forproducing contact lenses and also limit the choices of availablepolymerizable or crosslinkable material for making contact lenses.

A new class of additive, layer-based manufacturing processes has emergedthat enables “freeform manufacture” without the need for hard tooling(double-sided molding) or part-specific programming (machining).

Therefore, there still exists a need for a new method for economicallyproducing contact lenses without using the molding process. There alsoexists a need for a cost effective method of producing customizedcontact lenses.

SUMMARY OF THE INVENTION

The invention, in one aspect, provides a method for producing anophthalmic device by means of stereolithography. The method comprisesthe steps of: (a) depositing (i) an essentially solvent-free liquid ormelt of a device-forming material, or (ii) a solution of saiddevice-forming material, into a container comprising a single moldsurface, wherein said device-forming material is crosslinkable orpolymerizable by actinic radiation; (b) irradiating said device formingmaterial with one or more activation energy beams to obtain a curedlayer of polymerized or crosslinked device-forming material; (c)irradiating said device-forming material with said one or moreactivation energy beams to obtain a cured layer on top of a previouslycured layer with a back surface defined by the single male mold surface;and (d) repeating step (c) to obtain additional cured layers until saidophthalmic device is created integrally, wherein each of cured layerscorresponds to a pertinent section of said ophthalmic device.

The invention, in another aspect, provides a method for producing anophthalmic lens for a specific patient, comprising the steps of:receiving a prescription comprising a set of characteristic data of aneye of said patient; designing a 3-D mathematical model of theophthalmic lens based on the prescription; mathematically slicing the3-D mathematical model into a number of thin and vertically superimposedlayers, each layer having a defined thickness profile and a geometrycorresponding to a section (for example, a planar cross-section or acurved section) of the 3-D mathematical model at the level of thatlayer; and converting the thickness profile and the geometry of each ofa number of the thin and vertically superimposed layers into controlsignals that control a stereolithography machine to create, layer bysuperimposed layer over the single male mold surface, the ophthalmiclens in a bath of a crosslinkable or polymerizable device-formingmaterial.

The invention, in still another aspect, provides a system for producingan ophthalmic lens for a specific patient, comprising: a computersystem; a means in communication with said computer system for promptingthe patient or his eye care-practitioner, who takes care of the patient,to enter the prescription of an eye of the patient; a means fordesigning a 3-D mathematical model of the ophthalmic lens based on theprescription; a means for mathematically slicing the 3-D mathematicalmodel into a number of thin and vertically superimposed layers, eachlayer having a defined thickness profile and a geometry corresponding toa planar or curved section of the 3-D mathematical model at the level ofthat layer; a means for converting the thickness profile and thegeometry of each of a number of the thin and vertically superimposedlayers into control signals that control a stereolithography machine tocreate, layer by superimposed layer, the ophthalmic lens in a bath of acrosslinkable or polymerizable device-forming material.

The invention, in a further aspect, provides a computer program productfor use in a computer system to produce an ophthalmic lens by means ofstereolithography, comprising: a recording medium; means, recorded onthe recording medium, for designing a 3-D mathematical model of theophthalmic lens based on the prescription of an eye of a patient; means,recorded on the recording medium, for mathematically slicing the 3-Dmathematical model into a number of thin and vertically superimposedlayers, each layer having a defined thickness profile and a geometrycorresponding to a planar or curved section of the 3-D mathematicalmodel at the level of that layer; and means, recorded on the recordingmedium, for converting the thickness profile and the geometry of each ofa number of the thin and vertically superimposed layers into controlsignals that control a stereolithography machine to create, layer bysuperimposed layer, the ophthalmic lens in a bath of a crosslinkable orpolymerizable device-forming material, wherein said ophthalmic device isdefined by said thickness profile and the male mold surface.

One object of the invention is to provide a new method for manufacturingcontact lenses and other ophthalmic devices through the use of a singlemold.

Another object of the invention is to provide a lens production processthat can be easily adapted to making a customized contact lens in acost-effective manner.

A still object of the invention is to provide a lens production processthat can be easily adapted to the remote production of a contact lens oran ophthalmic device other than contact lens, preferably a customizedcontact lens, for example a made-to-order, cost-effective process forproducing customized contact lenses.

A further object of the invention is to provide a system for producing acontact lens, preferably a customized contact lens, according to a costeffective process.

These and other objects of the invention are met by the various aspectsof the invention described herein.

These and other aspects, features and advantages of the invention willbe understood with reference to the drawing figures and detaileddescription herein, and will be realized by means of the variouselements and combinations particularly pointed out in the appendedclaims. It is to be understood that both the foregoing generaldescription and the following brief description of the drawings anddetailed description of the invention are exemplary and explanatory ofpreferred embodiments of the invention, and are not restrictive of theinvention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram depicting the means for manufacturing anophthalmic device.

FIG. 2 a is a cross sectional view of an ophthalmic device as producedby the described process.

FIG. 2 b is a cross sectional view of a curved section (section A-A fromFIG. 2 a) through the ophthalmic device.

FIG. 2 c is a cross sectional view of a curved layer of an ophthalmicdevice that is based on the curved section in FIG. 2 b.

FIG. 2 d is a cross sectional view of an ophthalmic device formed by themanufacture of two curved layers from FIG. 2 c.

FIG. 3 shows a cross sectional view of an ophthalmic device asmanufactured by conventional stereolithography using verticallysuperimposed planar layers.

FIG. 4 is block diagram schematically depicting a system and method forproducing a pair of ophthalmic lens in a remote location for a specificpatient according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention may be understood more readily by reference to thefollowing detailed description of the invention taken in connection withthe accompanying drawing figures, which form a part of this disclosure.It is to be understood that this invention is not limited to thespecific devices, methods, conditions or parameters described and/orshown herein, and that the terminology used herein is for the purpose ofdescribing particular embodiments by way of example only and is notintended to be limiting of the claimed invention. Any and all patentsand other publications identified in this specification are incorporatedby reference as though fully set forth herein.

Also, as used in the specification including the appended claims, thesingular forms “a,” “an,” and “the” include the plural, and reference toa particular numerical value includes at least that particular value,unless the context clearly dictates otherwise. Ranges may be expressedherein as from “about” or “approximately” one particular value and/or to“about” or “approximately” another particular value. When such a rangeis expressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment.

The present invention is generally related to a new method for producinga contact lens or an ophthalmic device other than contact lens. Unlikeany methods known in the prior art for producing an ophthalmic device, amethod of the invention does not involve use of a complete male andfemale mold set and/or lathe in producing an ophthalmic device.According to a method of the invention, a stereolithography apparatus(machine) is used to produce an ophthalmic device, preferably a contactlens or a customized contact lens. Further, a single male mold is usedto form the posterior face of each lens.

An “ophthalmic device”, as used herein, refers to a contact lens (hardor soft), an intraocular lens, a corneal onlay, and other ophthalmicdevices (e.g., stents, implants, or the like) used on or about the eyeor ocular vicinity.

Stereolithography, as conventionally practiced, involves building, layerby superimposed layer, a three-dimensional (3-D) object, based on a 3-Dmathematical model of an object generated by a computer. The 3-Dmathematical model is typically generated with the help of 3-Dcomputer-aided design (CAD) software. The model is mathematicallyseparated or “sliced” into a large number of relatively thin andvertically superimposed layers, each layer having a defined thicknessprofile and a geometry corresponding to a planar cross-section of themodel at the level of that layer. The geometry of each layer definesboundaries and other features associated with the model at the level ofthat layer within the exterior boundaries of that object.

There are a variety of approaches to stereolithography depending upon amaterial employed to fabricate an object. A preferred stereolithographytechnique is based on polymerization and solidification of a liquidmaterial by actinic irradiation (e.g., a UV laser) one layer at a time.For example, a focused ultra-violet (UV) laser scans over the top of abath of a photopolymerizable liquid material following a pattern undercontrol of a computer or controller. The UV laser causes the bath topolymerize where the laser beam strikes the surface of the bath,resulting in the formation of a first solid plastic layer at and justbelow the surface. The solid layer is then lowered into the bath and thelaser-initiated polymerization process is repeated for the generation ofthe next layer, and so on, until a plurality of superimposed layers isobtained. Each of the solid plastic layers is a “reprint” of acorresponding “slice” (cross-section) of a 3-D mathematical model(design) of an object.

The present invention, in one aspect, provides a method for producing anophthalmic device by means of stereolithography. The method comprises:(a) depositing (i) an essentially solvent-free liquid or melt of adevice-forming material, or (ii) a solution of said device-formingmaterial, into a container comprising a mold, preferably a single mold,and more preferably a single male mold surface within the container,wherein said device-forming material is crosslinkable or polymerizableby actinic radiation; (b) irradiating said device forming material withone or more activation energy beams through the mold to obtain a curedlayer of polymerized or crosslinked device-forming material on the moldsurface; (c) irradiating said device-forming material with said one ormore activation energy beams to obtain a cured layer on top of apreviously cured layer, wherein the back side (first layer) of theophthalmic device is defined by the male mold surface; (d) repeatingstep (c) to obtain additional cured layers until said ophthalmic deviceis created integrally, wherein each of cured layers corresponds to apertinent slice of said ophthalmic device. Said container comprises amold, preferably a single mold, and more preferably a single male mold.

The present invention contemplates delivery of patterned actinicradiation to the device-forming material in order to form a layer of theophthalmic device. Programmed patterns of ultraviolet (UV) radiation areprojected through a male mold, which forms the lens' back surface,causing the device-forming material to cure into the desired shape of alens. A pattern generator, such as a Digital Micromirror Device (DMD™)from Texas Instruments, is used to generate the UV patterns. A DMD™ is alarge array of micromirrors that are individually addressable. UVradiation reflects off selected mirrors of the DMD™ through the malemold. By varying the patterns displayed on the pattern generator,different UV patterns are projected through the mold and into the lensmaterial, causing different lens thickness profiles to be cured.

A schematic of this embodiment is shown in FIG. 1. A digital model ofthe patient's vision correction needs is fed into the instrument'ssoftware 10 which computes a series of bitmap patterns to display on thepattern generator 12. Each layer of the ophthalmic device corresponds toone or more bitmap patterns. UV radiation 26 from a UV source 14, suchas a lamp or laser, is conditioned as needed, using suitable opticalelements, and is then reflected off of the pattern generator 12.Examples of preferred optical elements are a collimating lens 16 andiris or filter 18. It is also contemplated that a series of opticalelements can be used. From there, the UV radiation passes through afocusing (or diverging) lens 20 and the single mold 22, which focusesthe radiation. The mold may be comprised of a variety of materials, forexample quartz is preferred. The mold 22 preferably has a male shape.The irradiation time and the intensity profile of the radiation thatpasses into the ophthalmic photocurable device-forming material 24control the thickness of the cure at each point in the ophthalmicdevice. Each pattern displayed on the pattern generator 12 causes thedevice-forming material 24 to cure to a predetermined thickness profile.These patterns can be displayed individually or as a series, and with a“gray scale” defined by choosing the degree of defocusing, or blur, thatis introduced by controlling the position of the focusing lens 20. If asequence of patterns is to be used for a complex ophthalmic deviceshape, the series of patterns is carefully developed such that theresult of displaying them in sequence results in the precise ophthalmicdevice shape and thickness profile to yield the desired visioncorrection properties. Both spherical and specialty shaped ophthalmicdevices can be fabricated in this manner.

The use of the mold 22 is preferred for a variety of reasons. Firstly,it provides a precise surface on which the ophthalmic device can befabricated. Second, it acts as a lens for proper focusing of the UVradiation that causes resin curing. It is important to realize that theusage of the mold 22 does not impact the capability to fabricatecustomized ophthalmic devices. Molds with several different sizes andshapes are preferred, but the number can be less than 10. In contrast,using conventional ophthalmic device molding processes, thousands ofdifferent (female) molds are needed to provide the desired range ofophthalmic device corrective properties and shapes.

FIG. 2 a shows a cross sectional view of an ophthalmic device to beformed by the above described process. Such ophthalmic device ispreferred to be a contact lens. FIG. 2 b shows a curved section of theophthalmic device in FIG. 2A. The curved section in 2 b is arepresentation of one of the series of curved layers from which theophthalmic device is manufactured. FIG. 2 c is a single curved layer ofthe ophthalmic device of FIG. 2 a that is based on the curved section ofFIG. 2 b. Each layer is a product of one or more projected bitmappatterns. FIG. 2 d shows more than one curved layer of the ophthalmicdevice of FIG. 2 a that is based on the curve section of FIG. 2 b. Thenumber and thickness of layers used to construct a particular ophthalmicdevice is dependent upon the requirements of the individual user's eyeinput into the software 10 and projected from the UV generator 14.

The use of curved sections of an ophthalmic device is preferred, ratherthan the use of planar cross section of the ophthalmic device, aspracticed in conventional stereolithography. FIG. 3 shows the results ofmanufacturing an example ophthalmic device 28 using five planar layers30 from five planar cross sections. An alternative number of planarlayers is contemplated depending on the needs of the user. Themanufactured shape can only approximate the desired device shape, whichwill negatively impact its usage as a corrective lens.

In accordance with the present invention, a photocurable/crosslinkableor polymerizable device-forming material (hereinafter referred to as“device-forming material”) may be any of a wide variety of materialswhich can be polymerized and/or crosslinked by actinic radiation toobtain crosslinked materials which are ophthalmically compatible. Suchdevice-forming materials can be any materials known to a skilledartisan. For example, a device-forming material can be a compositionconsisting of primarily various monomers and/or macromers and optionallyfurther including various components, such as photoinitiator,inhibitors, fillers, and the like.

“Ophthalmically compatible”, as used herein, refers to a material orsurface of a material which may be in intimate contact with the ocularenvironment for an extended period of time without significantlydamaging the ocular environment and without significant user discomfort.Thus, an ophthalmically compatible contact lens will not producesignificant corneal swelling, will adequately move on the eye withblinking to promote adequate tear exchange, will not have substantialamounts of protein or lipid adsorption, and will not cause substantialwearer discomfort during the prescribed period of wear.

“Ocular environment”, as used herein, refers to ocular fluids (e.g.,tear fluid) and ocular tissue (e.g., the cornea) which may come intointimate contact with a contact lens used for vision correction, drugdelivery, wound healing, eye color modification, or other ophthalmicapplications.

A “monomer” means a low molecular weight compound that can bepolymerized. Low molecular weight typically means average molecularweights less than 700 Daltons.

A “macromer” refers to a medium and high molecular weight compound orpolymer that contains functional groups capable of furtherpolymerization. Medium and high molecular weight typically means averagemolecular weights greater than 700 Daltons.

Any suitable photoinitiator known to a person skilled in the art can beincorporated in a crosslinkable or polymerizable device-formingmaterial. Exemplary photoinitiators are benzoin-methylether,1-hydroxy-cyclo-hexyl-phenylketone, Darocure® 1173 or Irgacure® types.

A solution of a device-forming material can be prepared by dissolvingthe device-forming in any suitable solvent known to a person skilled inthe art. Examples of suitable solvents are water, alcohols, such aslower alkanols, for example ethanol or methanol, and furthermorecarboxylic acid amides, such as dimethylformamide, dipolar aproticsolvents, such as dimethyl sulfoxide or methyl ethyl ketone, ketones,for example acetone or cyclohexanone, hydrocarbons, for example toluene,ethers, for example THF, dimethoxyethane or dioxane, and halogenatedhydrocarbons, for example trichloroethane, and also mixtures of suitablesolvents, for example mixtures of water with an alcohol, for example awater/ethanol or a water/methanol mixture.

A preferred group of device-forming materials are ophthalmicallycompatible prepolymers which are water-soluble and/or meltable. It wouldbe advantageous that a device-forming material comprises primarily oneor more prepolymers which are preferably in a substantially pure form(e.g., purified by ultrafiltration). Therefore, after crosslinking byactinic radiation, an ophthalmic device may require practically no moresubsequent purification, such as in particular complicated extraction ofunpolymerized constituents. Furthermore, crosslinking may take placesolvent-free or in aqueous solution, so that a subsequent solventexchange or the hydration step is not necessary.

A “prepolymer” refers to a starting polymer which can be crosslinkedupon actinic radiation to obtain a crosslinked polymer having amolecular weight much higher than the starting polymer. Examples ofactinic radiation are UV irradiation, ionized radiation (e.g. gamma rayor X-ray irradiation), microwave irradiation, and the like.

A “polymer” means a material formed by polymerizing one or moremonomers.

One example of a preferred prepolymer is a water-soluble crosslinkablepoly(vinyl alcohol) prepolymer. More preferably, a water-solublecrosslinkable poly(vinyl alcohol) prepolymer is a polyhydroxyl compoundwhich is described in U.S. Pat. No. 5,583,163 (incorporated by referencein its entirety) and U.S. Pat. No. 6,303,687 (incorporated by referencein its entirety) and has a molecular weight of at least about 2000 andwhich comprises from about 0.5 to about 80%, based on the number ofhydroxyl groups in the poly(vinyl alcohol), of units of the formula I, Iand II, I and III, or I and II and III

A “molecular weight”, as used herein, refers to a weight averagemolecular weight, Mw, determined by gel permeation chromatography,unless otherwise specified.

In formula I, II and III, R₃ is hydrogen, a C₁-C₆ alkyl group or acycloalkyl group.

In formula I, II and III, R is alkylene having up to 12 carbon atoms,preferably up to 8 carbon atoms, and can be linear or branched. Suitableexamples include octylene, hexylene, pentylene, butylene, propylene,ethylene, methylene, 2-propylene, 2-butylene and 3-pentylene. Loweralkylene R preferably has up to 6, particularly preferably up to 4carbon atoms. Methylene and butylene are particularly preferred.

In the formula I, R₁ is hydrogen or lower alkyl having up to seven, inparticular up to four, carbon atoms. Most preferably, R₁ is hydrogen.

In the formula I, R₂ is an olefinically unsaturated,electron-withdrawing, crosslinkable radical, preferably having up to 25carbon atoms. In one embodiment, R₂ is an olefinically unsaturated acylradical of the formula R₄—CO—, in which R₄ is an olefinicallyunsaturated, crosslinkable radical having 2 to 24 carbon atoms,preferably having 2 to 8 carbon atoms, particularly preferably having 2to 4 carbon atoms.

The olefinically unsaturated, crosslinkable radical R₄ having 2 to 24carbon atoms is preferably alkenyl having 2 to 24 carbon atoms, inparticular alkenyl having 2 to 8 carbon atoms, particularly preferablyalkenyl having 2 to 4 carbon atoms, for example ethenyl, 2-propenyl,3-propenyl, 2-butenyl, hexenyl, octenyl or dodecenyl. Ethenyl and2-propenyl are preferred, so that the —CO—R₄ group is the acyl radicalof acrylic acid or methacrylic acid.

In another embodiment, the radical R₂ is a radical of the formula IV,preferably of the formula V

—CO—NH—(R₅—NH—CO—O)_(q)—R₆—O—CO—R₄   (IV)

—[CO—NH—(R₅—NH—CO—O)_(q)—R₆—O]_(p)—CO—R₄   (V)

in which p and q, independently of one another, are zero or one, and R₅and R₆, independently of one another, are lower alkylene having 2 to 8carbon atoms, arylene having 6 to 12 carbon atoms, a saturated bivalentcycloaliphatic group having 6 to 10 carbon atoms, arylenealkylene oralkylenearylene having 7 to 14 carbon atoms or arylenealkylenearylenehaving 13 to 16 carbon atoms, and in which R₄ is as defined above.

Lower alkylene R₅ or R₆ preferably has 2 to 6 carbon atoms and is, inparticular, linear. Suitable examples include propylene, butylene,hexylene, dimethylethylene and, particularly preferably, ethylene.

Arylene R₅ or R₆ is preferably phenylene, which is unsubstituted orsubstituted by lower alkyl or lower alkoxy, in particular 1,3-phenyleneor 1,4-phenylene or methyl-1,4-phenylene.

A saturated bivalent cycloaliphatic group R₅ or R₆ is preferablycyclohexylene or cyclohexylene(lower alkylene), for examplecyclohexylenemethylene, which is unsubstituted or substituted by one ormore methyl groups, for example trimethylcyclohexylenemethylene, forexample the bivalent isophorone radical.

The arylene unit of alkylenearylene or arylenealkylene R₅ or R₆ ispreferably phenylene, unsubstituted or substituted by lower alkyl orlower alkoxy, and the alkylene unit thereof is preferably loweralkylene, such as methylene or ethylene, in particular methylene.Radicals R₅ or R₆ of this type are therefore preferablyphenylenemethylene or methylenephenylene.

Arylenealkylenearylene R₅ or R₆ is preferably phenylene(loweralkylene)phenylene having up to 4 carbon atoms in the alkylene unit, forexample phenyleneethylenephenylene.

The radicals R₅ and R₆ are preferably, independently of one another,lower alkylene having 2 to 6 carbon atoms, phenylene, unsubstituted orsubstituted by lower alkyl, cyclohexylene or cyclohexylene(loweralkylene), unsubstituted or substituted by lower alkyl, phenylene(loweralkylene), (lower alkylene)phenylene or phenylene(loweralkylene)phenylene.

In the formula II, R₇ is a primary, secondary or tertiary amino group ora quaternary amino group of the formula N⁺(R′)₃X⁻, in which each R′,independently of the others, is hydrogen or a C₁-C₄ alkyl radical and Xis a counterion, for example HSO₄ ⁻, F⁻, Cl⁻, Br⁻, I⁻, CH₃COO⁻, OH⁻,BF⁻, or H₂PO₄ ⁻.

The radicals R₇ are, in particular, amino, mono- or di(loweralkyl)amino, mono- or diphenylamino, (lower alkyl)phenylamino ortertiary amino incorporated into a heterocyclic ring, for example —NH₂,—NH—CH₃, —N(CH₃)₂, —NH(C₂H₅), —N(C₂H₅)₂, —NH(phenyl), —N(C₂H₅)phenyl or

In the formula III, R₈ is the radical of a monobasic, dibasic ortribasic, saturated or unsaturated, aliphatic or aromatic organic acidor sulfonic acid. Preferred radicals R₈ are derived, for example, fromchloroacetic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, maleic acid, fumaric acid, itaconic acid, citraconic acid, acrylicacid, methacrylic acid, phthalic acid and trimellitic acid.

For the purposes of this invention, the term “lower” in connection withradicals and compounds denotes, unless defined otherwise, radicals orcompounds having up to 7 carbon atoms, preferably having up to 4 carbonatoms.

Lower alkyl has, in particular, up to 7 carbon atoms, preferably up to 4carbon atoms, and is, for example, methyl, ethyl, propyl, butyl ortert-butyl.

Lower alkoxy has, in particular, up to 7 carbon atoms, preferably up to4 carbon atoms, and is, for example, methoxy, ethoxy, propoxy, butoxy ortert-butoxy.

The bivalent group —R₅—NH—CO—O— is present if q is one and absent if qis zero. Poly(vinyl alcohol)s containing crosslinkable groups in which qis zero are preferred.

The bivalent group —CO—NH—(R₅—NH—CO—O)q-R₆—O— is present if p is one andabsent if p is zero. Poly(vinyl alcohol)s containing crosslinkablegroups in which p is zero are preferred.

In the poly(vinyl alcohol)s comprising units containing crosslinkablegroups in which p is one, the index q is preferably zero. Particularpreference is given to poly(vinyl alcohol)s comprising crosslinkablegroups in which p is one, the index q is zero and R₅ is lower alkylene.

In the formula N⁺(R′)₃X⁻, R′ is preferably hydrogen or C₁-C₃ alkyl, andX is halide, acetate or phosphite, for example —N⁺(C₂H₅)₃CH₃COO—,—N⁺(C₂H₅)₃Cl⁻, and —N⁺(C₂H₅)₃H₂PO₄ ⁻.

A water-soluble crosslinkable poly(vinyl alcohol) according to theinvention is more preferably a polyhydroxyl compound which has amolecular weight of at least about 2000 and which comprises from about0.5 to about 80%, preferably from 1 to 50%, more preferably from 1 to25%, even more preferably from 2 to 15%, based on the number of hydroxylgroups in the poly(vinyl alcohol), of units of the formula I, wherein Ris lower alkylene having up to 6 carbon atoms, R₁ is hydrogen or loweralkyl, R₃ is hydrogen, and R₂ is a radical of formula (V). Where p iszero, R₄ is preferably C₂-C₈ alkenyl. Where p is one and q is zero, R₆is preferably C₂-C₆ alkylene and R₄ is preferably C₂-C₈ alkenyl. Whereboth p and q are one, R₅ is preferably C₂-C₆ alkylene, phenylene,unsubstituted or lower alkyl-substituted cyclohexylene or cyclohexylene-lower alkylene, unsubstituted or lower alkyl-substitutedphenylene-lower alkylene, lower alkylene-phenylene, or phenylene-loweralkylene-phenylene, R₆ is preferably C₂-C₆ alkylene, and R₄ ispreferably C₂-C₈ alkenyl.

Crosslinkable poly(vinyl alcohol)s comprising units of the formula I, IIand II, I and III, or I and II and III can be prepared in a manner knownper se. For example, U.S. Pat. No. 5,583,163 (incorporated by referencein its entirety) and U.S. Pat. No. 6,303,687 (incorporated by referencein its entirety) disclose and teach how to prepare crosslinkablepolymers comprising units of the formula I, I and II, I and III, or Iand II and III.

Another example of a preferred prepolymer according to the invention isa vinyl group-terminated polyurethane which is obtained by reacting anisocyanate-capped polyurethane with an ethylenically unsaturated amine(primary or secondary amine) or an ethylenically unsaturated monohydroxycompound. The isocyanate-capped polyurethane is a copolymerizationproduct of

-   (a) at least one polyalkylene glycol of formula

HO—(R₉—O)_(n)—(R₁₀—O)_(m)—(R₁₁—O)_(l)—H   (1)

wherein R₉, R₁₀, and R₁₁, independently of one other, are each linear orbranched C₂-C₄-alkylene, and n, m and l, independently of one another,are each a number from 0 to 100, wherein the sum of (n+m+l) is 5 to 100,

-   (b) at least one branching agent selected from the group consisting    of    -   (i) a linear or branched aliphatic polyhydroxy compound of        formula

R₁₂—(OH)_(x)   (2),

-   -    wherein R₁₂ is a linear or branched C₃-C₁₈ aliphatic        multi-valent radical and x is a number ≧3,    -   (ii) a polyether polyol, which is the polymerization product of        a compound of formula (2) and a glycol,    -   (iii) a polyester polyol, which is the polymerization product of        a compound of formula (2), a dicarboxylic acid or a derivative        thereof and a diol, and    -   (iv) a cycloaliphatic polyol selected from the group consisting        of a C₅-C₈-cycloalkane which is substituted by ≧3 hydroxy groups        and which is unsubstituted by alkyl radical, a C₅-C₈-cycloalkane        which is substituted by ≧3 hydroxy groups and which is        substituted by one ore more C₁-C₄ alkyl radicals, and an        unsubstituted mono- and disaccharide,    -   (v) an aralkyl polyol having at least three hydroxy C₁-C₄ alkyl        radicals, and

-   (c) at least one di- or polyisocyanate of formula

R₁₃—(NCO)_(y)   (3)

wherein R₁₃ a linear or branched C₃-C₂₄ aliphatic polyisocyanate, theradical of a C₃-C₂₄ cycloaliphatic or aliphatic-cycloaliphaticpolyisocyanate, or the radical of a C₃-C₂₄ aromatic or araliphaticpolyisocyanate, and y is a number from 2 to 6.

The isocayanate-capped polyurethane polymers according to the inventionmay be produced by following a solventless process. For example, in asolventless process, first one or more polyalkylene glycols of formula(1) (component (a)) is mixed with one or more branching agents(component (b)) and the mixture is heated to and maintained at a meltingtemperature or above. Then, at least one di- or polyisocyanate offormula (3) (component (c)) is added to the melted mixture to make amelted reaction mixture comprising component (a), component (b) andcomponent (c) in a desired stoichiometry. The temperature of the meltedreaction mixture is continuously and thoroughly stirred at the meltingtemperature or above and preferably under an inert atmosphericenvironment (for example, in nitrogen or argon atmosphere). Reaction ismonitored by, for example, monitoring the isocyanate peak in FT-IRspectroscopy. Components (a)-(c) are all known compounds or compoundmixtures, or may be obtained in accordance with methods known per se.

A further example of a preferred prepolymer is a crosslinkable polyureaprepolymer as described in European patent No. 1,017,734, incorporatedby reference in its entirety. The crosslinkable polyurea prepolymer canbe obtained by reacting an acryloylchloride or an isocyanategroup-containing carylate or methacrylate with a polymerization productof NH₂-terminated polyalkylene glycols and di- or polyisocyanatesoptionally in the presence of a triamine.

Other exemplary preferred prepolymers include: crosslinkable statisticalcopolymers of vinyl lactam, MMA and a comonomer, which are disclosed inEP 655,470 (incorporated by reference in its entirety) and U.S. Pat. No.5,712,356 (incorporated by reference in its entirety); crosslinkablecopolymers of vinyl lactam, vinyl acetate and vinyl alcohol, which aredisclosed in EP 712,867 (incorporated by reference in its entirety) andU.S. Pat. No. 5,665,840 (incorporated by reference in its entirety);polyether-polyester copolymers with crosslinkable side chains which aredisclosed in EP 932,635 (incorporated by reference in its entirety);branched polyalkylene glycol-urethane prepolymers disclosed in EP958,315 (incorporated by reference in its entirety) and U.S. Pat. No.6,165,408 (incorporated by reference in its entirety); polyalkyleneglycol-tetra(meth)acrylate prepolymers disclosed in EP 961,941(incorporated by reference in its entirety) and U.S. Pat. No. 6,221,303(incorporated by reference in its entirety); and crosslinkablepolyallylamine gluconolactone prepolymers disclosed in PCT patentapplication WO 2000/31150 (incorporated by reference in its entirety).

In accordance with a preferred embodiment of the invention, adevice-forming material is composed of primarily one or more prepolymersand optionally additional vinylic monomers. Photocuring/Crosslinking orpolymerizing is preferably effected whilst solvent-free or essentiallysolvent-free or directly from an aqueous solution. The prepolymer ispreferably in a substantially pure form, for example, as obtained by apurification step, such as ultrafiltration. For example, crosslinking orpolymerizing may be undertaken from an aqueous solution containing about15 to 90% of one or more prepolymers.

The vinylic monomer which may be additionally used forphoto-crosslinking or polymerizing in accordance with the invention maybe hydrophilic, hydrophobic or may be a mixture of a hydrophobic and ahydrophilic vinylic monomer. Suitable vinylic monomers includeespecially those normally used for the manufacture of contact lenses. A“hydrophilic vinylic monomer” refers to a monomer which as a homopolymertypically yields a polymer that is water-soluble or can absorb at least10 percent by weight water. A “hydrophobic vinylic monomer” refers to amonomer which as a homopolymer typically yields a polymer that isinsoluble in water and can absorb less than 10 percent by weight water.

It is preferable to use a hydrophobic vinylic monomer, or a mixture of ahydrophobic vinylic monomer with a hydrophilic vinylic monomer, wherebythis mixture contains at least 50 percent by weight of a hydrophobicvinyl comonomer. In this way, the mechanical properties of the resultantpolymer may be improved without the water content droppingsubstantially. Both conventional hydrophobic vinylic monomers andconventional hydrophilic vinylic monomers are suitable forcopolymerization with the prepolymers.

Suitable hydrophobic vinylic monomers include, without limitation,C₁-C₁₈-alkylacrylates and -methacrylates, C₃-C₁₈ alkylacrylamides and-methacrylamides, acrylonitrile, methacrylonitrile,vinyl-C₁-C₁₈-alkanoates, C₂-C₁₈-alkenes, C₂-C₁₈-halo-alkenes, styrene,C₁-C₆-alkylstyrene, vinylalkylethers in which the alkyl moiety has 1 to6 carbon atoms, C₂-C₁₀-perfluoralkyl-acrylates and -methacrylates orcorrespondingly partially fluorinated acrylates and methacrylates,C₃-C₁₂-perfluoralkyl-ethyl-thiocarbonylaminoethyl-acrylates and-methacrylates, acryloxy and methacryloxy-alkylsiloxanes,N-vinylcarbazole, C₁-C₁₂-alkylesters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given e.g. toC₁-C₄-alkylesters of vinylically unsaturated carboxylic acids with 3 to5 carbon atoms or vinylesters of carboxylic acids with up to 5 carbonatoms.

Examples of suitable hydrophobic vinylic monomers includemethylacrylate, ethyl -acrylate, propylacrylate, isopropylacrylate,cyclohexyl acrylate, 2-ethylhexylacrylate, methylmethacrylate,ethylmethacrylate, propylmethacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyl toluene, vinyl ethyl ether,perfluorohexylethyl-thio-carbonyl-aminoethyl-methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoro-isopropylmethacrylate, hexafluorobutyl methacrylate,tris-trimethylsilyloxy-silyl-propyl methacrylate,3-methacryloxypropyl-pentamethyl-disiloxane andbis(methacryloxypropyl)-tetramethyl-disiloxane.

Suitable hydrophilic vinylic monomers include, without limitation,hydroxy-substituted lower alkylacrylates and -methacrylates, acrylamide,methacrylamide, lower alkyl-acrylamides and -methacrylamides,ethoxylated acrylates and methacrylates, hydroxy-substituted loweralkyl-acrylamides and -methacrylamides, hydroxy-substituted loweralkylvinyl-ethers, sodium ethylene sulphonate, sodium styrenesulphonate, 2-acrylamido-2-methyl-propane-sulphonic acid, N-vinylpyrrole, N-vinyl succinimide, N-vinyl pyrrolidone, 2- or 4-vinylpyridine, acrylic acid, methacrylic acid, amino- (whereby the term“amino” also includes quaternary ammonium), mono-lower-alkylamino- ordi-lower-alkylamino-lower-alkyl-acrylates and -methacrylates, allylalcohol and the like. Preference is given e.g. to hydroxy-substitutedC₂-C₄-alkyl(meth)acrylates, five- to seven-membered N-vinyl-lactams,N,N-di-C₁-C₄-alkyl-methacrylamides and vinylically unsaturatedcarboxylic acids with a total of 3 to 5 carbon atoms.

Examples of suitable hydrophilic vinylic monomers include hydroxyethylmethacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide,dimethylacrylamide, allyl alcohol, vinyl pyridine, vinyl pyrrolidone,glycerol methacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide, and thelike.

Preferred hydrophobic vinylic monomers are methyl methacrylate and vinylacetate. Preferred hydrophilic vinylic comonomers are 2-hydroxyethylmethacrylate, N-vinyl pyrrolidone and acrylamide.

In accordance with the invention, each of cured layers (solidifiedplastic or hydrogel layers) is preferably have a thickness of less thanabout 20 mils (mili-inches), more preferably less than about 10 mils,even more preferably less than 6 mils, most preferably less than 4 mils.

The thickness of a cure layer is largely controlled by two properties ofa device-forming material, the critical exposure (E_(c)) and the depthof penetration (D_(p)).

E_(c) is defined as the minimum amount of exposure to cause a sufficientnumber of reactions to form gel. Exposure (E) is defined as the amountof energy striking a surface and measured in term of energy/areaooules/cm²). E_(c) is material and wavelength dependent. If adevice-forming material receives more exposure than E_(c), the gelledmass polymerizes more and the mass becomes stronger until the point isreached that sufficient exposure has been given to complete thepolymerization process. E_(c) of a device-forming material can bechanged by adding one or more photoinitiators or radical scavengers(inhibitors).

D_(p) is the depth of a device-forming material into which an actinicradiation can penetrate. The depth of penetration is inversely relatedto a device-forming material's ability to absorb radiation and isgenerally wavelength dependent. The depth of penetration of adevice-forming material can be adjusted by adding one or more UVabsorbing agents. By increasing the concentration of a UV absorbingagent in a device-forming material, the depth of penetration can bedecreased.

In accordance with the invention, the thickness of a cure layer can becontrolled by controlling the irradiance from the radiation source inrelation to D_(p) and E_(c). For example, where a device-formingmaterial has a relatively small E_(c), a laser beam can scan the bathsurface at a relatively higher speed to obtain a thinner cured layer,since the exposure needed to cause polymerization is relatively smaller.Since actinic radiation becomes more and more attenuated as it goesdeeper and deeper into the device-forming material, the upper level (atthe bath surface and just below the surface) receives greater intensity,and thus great exposure, than the lower level. Thus, the upper levelswill gel whereas the device-forming material at lower levels has not yetgelled.

In a preferred embodiment, a device-forming material comprises at leastone UV absorbing agent at a concentration sufficient to reduce the depthof penetration of the device-forming material to a desired D_(p). It isadvantageous to add UV absorbing agents to a device-forming material.This can incorporate the UV absorbing agents into the resultant contactlens or intraocular lens, as is known in the art. UV absorbing agentsare capable of minimizing the UV-associated damage to an eye. ExemplaryUV absorbing agents include, but are not limited to, 4-methacryloxy2-hydroxybenzophenone (MOBP), 2-(3′-methallyl-2′-hydroxy-5′-methylphenyl)benzotriazole, substituted 2-hydroxybenzophenones,2-hydroxy-5-acryloxyphenyl-2H-benzotriazoles, and the like.

Activation energy beams can be electron beams, X-rays, or preferably UVor visible lights. Suitable light sources include, but are not limitedto, He:Cd laser, argon-ion laser, nitrogen laser, metal vapor laser,Nd:YAG laser. A laser can produce a single line at one wavelength linesor several lines at several wavelengths. For example, commercial HeCdlasers produce a single wavelength line at 325 nm. A commercialargon-ion laser can be set to lase in the UV region at a variety ofsingle wavelength or at several wavelengths simultaneously. The primaryUV lines for the argon-ion laser are at approximately 364 nm, 252 nm,and 334 nm, and others. The laser can be set to lase at all thesewavelengths simultaneously with power outputs of about 40%, 40%, and 20%for the 364 nm line, the 351 nm line, and 334 nm line/other linesrespectively.

In another preferred embodiment of the invention, two activation energybeams are employed to obtain cured layers, wherein these energy beamshave different wavelengths and can produce two different values of depthof penetration of a device-forming material. An energy beam, whichproduces a smaller D_(p) value, is used to scan the peripheral edges ofa layer to minimize the emergence of sharp layer boundaries, so that anophthalmic device with a relatively smooth surface can be obtained.Alternatively, two identical energy beams, a first and a second beam,can be used in a method of the invention. In this embodiment, thedevice-forming material 24 gels only where the two beams intersect,which is a method of improving the resolution of the manufacturingprocess. Typically, the two beams will enter the device-forming material24 at different angles, preferably with an angular difference largerthan 30 degrees in order to provide a properly controlled intersectionregion where the device-forming material 24 will gel. It is to beunderstood that one or both of the energy beams may enter thedevice-forming material 24 through the mold 22. The energy beams mayalso enter the device-forming material 24 through the top of thedevice-forming material container.

In the preferred embodiment, patterns of radiation are created by apattern generator 12. In an alternate embodiment, radiation patterns canbe produced by scanning of an energy beam over the surface of the bathor the mold. Both the generation of bitmap patterns for the patterngenerator or the scanning of an energy beam are controlled by a computeror controller to follow a desired pattern. Such computer control istypically effected by control signals, which are converted from a 3-Dmathematical model of an ophthalmic device. The conversion processinvolves mathematically separating or “slicing” the 3-D mathematicalmodel into a number of relatively thin and vertically superimposedlayers, each layer having a defined thickness profile and a geometrycorresponding to a planar or curved section of the model at the level ofthat layer.

Typically, a 3-D mathematical model of an ophthalmic device is generatedwith the help of a CAD software. A person skilled in the art knows howto design an ophthalmic device and then construct the mathematicalsurfaces of the design to obtain the 3-D mathematical model. Forexample, a contact lens having any surface designs includingnon-rotationally-symmetric surfaces can be designed by using an opticalcomputer aided design (CAD) system and a mechanical CAD system.

An optical CAD system is used to design an optical model lens. “Anoptical model lens” refers to a contact lens that is designed in acomputer system and generally does not contain other non-optical systemswhich are parts of the contact lens. Exemplary non-optical systems of acontact lens include, but are not limited to bevel, lenticular, and edgethat joins the anterior and posterior surfaces of a contact lens.

“A bevel” refers to a non-optical surface zone located at the edge ofthe posterior surface of a contact lens. Generally, the bevel is asignificantly flatter curve and is usually blended with the base curve(optical posterior surface) of a contact lens and appears as an upwardtaper near the edge. This keeps the steeper base curve radius fromgripping the eye and allows the edge to lift slightly. This edge lift isimportant for the proper flow of tears across the cornea and makes thelens fit more comfortably.

“A lenticular” refers to a non-optical surface zone of the anteriorsurface of a contact lens between the optical zone and the edge. Theprimary function of the lenticular is to control the thickness of thelens edge.

Any known, suitable optical computer aided design (CAD) system may beused to design an optical model lens. Exemplary optical computer aideddesign systems includes, but are not limited to Advanced System Analysisprogram (ASAP) from Breault Research Organization and ZEMAX (FocusSoftware, Inc.). Preferably, the optical design will be performed usingAdvanced System Analysis program (ASAP) from Breault ResearchOrganization with input from ZEMAX (Focus Software, Inc.).

The design of the optical model lens can be transformed by, for example,a mechanical CAD system, into a mechanical lens design that includesoptical zones, non-optical zones and non-optical features. Exemplarynon-optical zones and features of a contact lens include, but are notlimited to bevel, lenticular, edge that joins the anterior and posteriorsurfaces of a contact lens, orientation features, and the like.Exemplary orientation features include, but are not limited to, a prismballast or the like that uses a varying thickness profile to control thelens orientation, a faceted surface (e.g., ridge-off zone) in whichparts of the lens geometry is removed to control the lens orientation, aridge feature which orients the lens by interacting with the eyelid.Preferably, when transforming the design of an optimized optical modellens into a mechanical lens design, some common features of a family ofcontact lenses can be incorporated.

Any known, suitable mechanical CAD system can be used in the invention.Preferably, a mechanical CAD system capable of representing preciselyand mathematically high order surfaces is used to design a contact lens.An example of such mechanical CAD system is Pro/Engineer.

Preferably, the design of a contact lens may be translated back andforth between the optical CAD and mechanical CAD systems using atranslation format which allows a receiving system, either optical CADor mechanical CAD, to construct NURBs or Beizier surfaces of an intendeddesign. Exemplary translation formats include, but are not limited to,VDA (verband der automobilindustrie) and IGES (Initial Graphics ExchangeSpecification). By using such translation formats, overall surface oflenses can be in a continuous form that facilitates the production oflenses having radially asymmetrical shapes.

Any mathematical function can be used to describe the anterior surface,posterior surface or peripheral edge of an ophthalmic lens, as long asthey have sufficient dynamic range which allow the design of that lensto be optimized. Exemplary mathematical functions include conic andquadric functions, polynomials of any degree, Zernike polynomials,exponential functions, trigonometric functions, hyperbolic functions,rational functions, Fourier series, and wavelets. Preferably, acombination of two or more mathematical functions are used to describethe front (anterior) surface and base (posterior) surface of anophthalmic lens. More preferably, Zernike polynomials are used todescribe the front (anterior) surface and base (posterior) surface of anophthalmic lens. Even more preferably, Zernike polynomials andspline-based mathematical functions are used together to describe thefront (anterior) surface and base (posterior) surface of an ophthalmiclens.

After the optical and mechanical design for a contact lens is completed,a lens design (a 3-D mathematical model) is typically in a neutral fileformat, for example, such as IGES or VDA, or in a proprietary fileformat (for example, a Pro/E file format). The lens design is thenmathematically separated or sliced into a large number of thin andvertically superimposed layers, each layer having a defined thicknessprofile and a geometry corresponding to a planar or curved section ofthe lens model at the level of that layer. Then, the thickness profileand the geometry of each of a number of the thin and verticallysuperimposed layers are converted into control signals which willcontrol activation energy beams to print, one at a time, each of anumber of the thin and vertically superimposed layers. “Vertically” inreference to a contact lens means a direction parallel to the centralaxis of the contact lens. The central axis of a contact lens refers to aline that passes through the apex of the anterior surface (convexcurvature surface) of the contact lens in a normal direction to thesurface.

What is notable about a method of the invention is that the contactlenses according to the invention can be produced from aphotocurable/crosslinkable or polymerizable device-forming material in avery simple and efficient way compared with the prior art. This is basedon many factors. On the one hand, neither complete mold sets nor lathesare involved in the production. The cost associated with molds can beeliminated. Secondly, there are no stringent manufacturing requirementsrelated to dispensing of essentially solvent-free liquid or melt of adevice-forming material or of a solution of said device-formingmaterial. The solution or essentially solvent-free liquid or melt of adevice-forming material can have a wide range of viscosity.

It would be advantageous that a device-forming material comprisesprimarily one or more prepolymers which are preferably in asubstantially pure form (e.g., purified by ultrafiltration). Therefore,after crosslinking by actinic radiation, an ophthalmic device mayrequire practically no more subsequent purification, such as inparticular complicated extraction of unpolymerized constituents.Furthermore, crosslinking may take place solvent-free or in aqueoussolution, so that a subsequent solvent exchange or the hydration step isnot necessary.

What is also notable about the method of the invention is that, togetherwith a communication network, such as the Internet, a method of theinvention based on stereolithography can be easily and economicallyimplemented to produce a customized contact lens or to produce anycontact lens in a remote location, for example, in the office of aneye-doctor or decentralized production facilities. It is also conduciveto conduct electronic business involving ordering, making and deliveringof contact lenses.

A “customized contact lens” refers to a contact lens made to order.

The Internet comprises a vast number of computers and computer networksthat are interconnected through communication links. The interconnectedcomputers exchange information using various services, such aselectronic mail, Gopher, and the World Wide Web (“WWW”). The WWW serviceallows a server computer system (i.e., Web server or Web site) to sendgraphical Web pages of information to a remote client computer system.The remote client computer system can then display the Web pages. Eachresource (e.g., computer or Web page) of the WWW is uniquelyidentifiable by a Uniform Resource Locator (“URL”). To view a specificWeb page, a client computer system specifies the URL for that Web pagein a request (e.g., a HyperText Transfer Protocol (“HTTP”) request). Therequest is forwarded to the Web server that supports that Web page. Whenthat Web server receives the request, it sends that Web page to theclient computer system. When the client computer system receives thatWeb page, it typically displays the Web page using a browser. A browseris a special-purpose application program that effects the requesting ofWeb pages and the displaying of Web pages.

Currently, Web pages are typically defined using HyperText MarkupLanguage (“HTML”). HTML provides a standard set of tags that define howa Web page is to be displayed. When a user indicates to the browser todisplay a Web page, the browser sends a request to the server computersystem to transfer to the client computer system an HTML document thatdefines the Web page. When the requested HTML document is received bythe client computer system, the browser displays the Web page as definedby the HTML document. The HTML document contains various tags thatcontrol the displaying of text, graphics, controls, and other features.The HTML document may contain URLs of other Web pages available on thatserver computer system or other server computer systems.

The present invention, in another aspect, provides a method forproducing an ophthalmic lens for a specific patient. The methodcomprises: receiving a prescription comprising a set of characteristicdata of an eye of said patient; designing a 3-D mathematical model ofthe ophthalmic lens based on the prescription; mathematically slicingthe 3-D mathematical model into a number of thin and verticallysuperimposed layers, each layer having a defined thickness profile and ageometry corresponding to a cross-section of the 3-D mathematical modelat the level of that layer; and converting the thickness profile and thegeometry of each of a number of the thin and vertically superimposedlayers into control signals that control a stereolithography machine tocreate, layer by superimposed layer, the ophthalmic lens in a bath of acrosslinkable or polymerizable device-forming material.

The prescription of an eye minimally comprises low-order aberrations ofthe eye, such as defocus, astigmatism and prism, and optionally theappropriate curvature of the posterior surface (concave surface).Preferably, the prescription of an eye comprises wavefront aberrationsof the eye and/or corneal topography data of the eye.

The wavefront aberrations of an eye of an individual can be determinedby any suitable methods known to one skilled in the art. For example,Liang et al. in J. Optical Soc. Am. 11:1-9, the entirety of which areherein incorporated by reference, teach how to determine wavefrontaberrations of an eye at various pupil diameters using a Hartmann-Shacksystem. The wavefront aberrations generally are quantified in Zernikepolynomials which are a set of functions that are orthogonal over theunit circle. Since Zernike polynomials are orthogonal, the aberrationsare separable and can be treated as such. The first order Zernike modesare the linear terms. The second order Zernike modes are the quadraticterms, which correspond to the aberrations such as defocus andastigmatism. The third order Zernike modes are the cubic terms, whichcorrespond to the coma and coma-like aberrations. The fourth orderZernike modes contain spherical aberrations as well as other modes. Thefifth Zernike modes are the higher-order, irregular aberrations. Localirregularities in the wavefront within the pupil are represented bythese higher-order Zernike modes.

“High-order” aberrations of an eye as used herein refers tomonochromatic aberrations beyond defocus and astigmatism, namely, thirdorder, fourth order, fifth order, and higher order wavefrontaberrations.

Corneal topographic data can be acquired using a corneal topographer orvideokeratoscope. Corneal topography data may be in any forms suitablefor use in designing an ophthalmic lens. Exemplary forms include, butare not limited to, Zernike polynomials, point cloud data and the like.Preferably, corneal topography data is in a form in which the wavefrontaberrations of an eye are quantified. The corneal topography datacontained in the set of characteristic data of an eye can also be anaveraged corneal topography derived from population studies.

The steps of designing, mathematically slicing and converting areperformed in a computer system, which is linked, via interface, to acustomer (a patient or an eye-care practitioner). The interface betweenthe computer system and the customer can be any conventional interface,such as internet, network, wide area network, point-to-point dial upconnection, hard wire link, wireless link, and the like. Lesspreferably, the interface is a manual communication means, such as, forexample, a paper copy of the prescription, which is transmitted by faxor mail or hand delivered to a computer operator who enters informationinto the computer using, for example, a keyboard, touch screen, voicerecognition hardware and software, or scanner.

In a preferred embodiment of the invention, the method for producing anophthalmic lens for a specific patient further comprises a step ofmaking available the control signals for the production of theophthalmic lens. In this embodiment, the control signals can be directlycommunicated from the computer to the customer via the interfacedescribed above, or less preferably the control signals are recorded ina computer-readable medium which is mailed to or hand delivered to thecustomer.

FIG. 4 is a block diagram illustrating a preferred embodiment of theinvention. This preferred embodiment provides a method for producing apair of ophthalmic lenses in a remote location for a specific patientover the Internet using the World Wide Web.

Referring to FIG. 4, a server system 110 comprises a server engine 111,a lens design engine 113, a query engine 112, a stereolithography engine114, a customer identifier table 122, various Web pages 121, a patientdatabase 131, an eye-care practitioner database 132, and a SKU database133.

The server engine 111 receives HTTP requests to access Web pagesidentified by URLs and provides the Web pages to the various customercomputer systems. The server engine also assigns and sends a customeridentifier to a customer computer system once when the customer computersystem first interacts with the server system. The customer computersystem then includes its customer identifier with all messages sent tothe server system so that the server system can identify the source ofthe message.

The lens design engine 113 is a computer program that designs the 3-Dmathematical models of a pair of ophthalmic lenses on the basis of theprescription of the eyes of the patient. The prescription preferablycomprises the wavefront aberrations and corneal topographies of the eyesof an individual. The lens design engine 113 can generate a set ofphysical and optical parameters for this pair of ophthalmic lensesoptimized for accommodating the corneal topographies and for correctingaberrations. Such set of physical and optical parameters can be used toproduce a new pair of customized lens or be utilized by the query engine112, that is a computer program, to search against a SKU database whichcontains all previously designed ophthalmic lenses. The query engineemploys an algorithm to find for each of the two eyes a list of SKUseach of which can adequately accommodate the corneal topography of thateye and adequately correct the aberrations of that eye. Such lists ofSKUs with lens information, such as one or more crosslinkable orpolymerizable device-forming material, the conformity of each lens tothe corneal topography of the corresponding eye, and a reachable visualacuity with a specific SKU. Preferably, the conformity of each lens tothe corneal topography of the corresponding eye is displayed in acustomer computer system as an interactive three-dimensional graphicrepresentation and the reachable visual acuity with a specific SKU isdisplay in the same computer system as a graphic representation, forexample, a simulated retina image quality. The patient can select onecrosslinkable or polymerizable device-forming material and one pair ofSKUs or can request to design a new pair of ophthalmic lenses.

“A contact lens can correct adequately the aberrations of an eye”, asused herein, means that the lens can correct the aberrations of the eyeat least to the extent as prescribed by an eye-care practitioner.

The stereolithography engine 114 is a computer program thatmathematically slices the 3-D mathematical model of an ophthalmic lensinto a number of thin and vertically superimposed layers, each layerhaving a defined thickness profile and a geometry corresponding to aplanar or curved section of the 3-D mathematical model at the level ofthat layer, and that converts the thickness profile and the geometry ofeach of a number of the thin and vertically superimposed layers intocontrol signals that control a stereolithography machine to create,layer by superimposed layer, the ophthalmic lens in a bath of acrosslinkable or polymerizable device-forming material. The generatedcontrol signals then will be sent to the customer computer system 140which controls a stereolithography machine (not shown) to produce a pairof ophthalmic lenses.

The patient database 131 contains patient-specific order information,such as name of the patient, and billing information for variouspatients or potential patients.

The eye-care practitioner database 132 contains eye-carepractitioner-specific order information, such as name of the patientunder the eye-care practitioner's care, and address and contactinformation of the eye-care practitioner, for various patients orpotential patients.

The customer identifier table 122 contains a mapping from each customeridentifier, which is a globally unique identifier that uniquelyidentifies a customer computer system, to the patient or eye-carepractitioner last associated with that customer computer system.

The customer computer system 140 comprises a browser 141, an assignedcustomer identifier 142, and input/output (I/O) interface devices. Thecustomer identifier is stored in a file, referred to as a “cookie.” Aninput device receives input (such as data, commands, etc.) from humanoperators and forwards such input to the customer computer system 140via a communication medium. Any known, suitable input device may be usedin the present invention, such as a keyboard, pointing device (mouse,roller ball, track ball, light pen, etc.), touch screen, etc. User inputmay also be stored and then retrieved, as appropriate, from data/commandfiles. An output device outputs information to human operators. Thecustomer computer system transfers such information to the output devicevia a communication medium. Any well known, suitable output device maybe used in the present invention, such as a monitor, a printer, a floppydisk drive, a text-to-speech synthesizer, etc. In a more preferredembodiment, a sensor system, that can measure at least wavefrontaberrations, preferably at least wavefront aberrations and cornealtopography of the eyes of an individual, is connected to the customercomputer system via a communication medium.

The customer computer system may comprise any combination of hardwareand software that can interact with the server system. One example is acustomer computer system comprising a television-based system.

It will be understood that the method of the invention for producing apair of ophthalmic lens in a remote location for a specific patient canbe implemented in various environments other than the Internet.Exemplary environments other than the Internet include, but are notlimited to, an electronic mail environment, local area network, widearea network, and point-to-point dial up connection.

The present invention, in still another aspect, provides a system forproducing an ophthalmic lens for a specific patient, comprising: acomputer or a computer system; a means in communication with saidcomputer or computer system for prompting the patient or his eyecare-practitioner, who takes care of the patient, to enter theprescription of an eye of the patient; a means for designing a 3-Dmathematical model of the ophthalmic lens based on the prescription; ameans for mathematically slicing the 3-D mathematical model into anumber of thin and vertically superimposed layers, each layer having adefined thickness profile and a geometry corresponding to a planar orcurved section of the 3-D mathematical model at the level of that layer;a means for converting the thickness profile and the geometry of each ofa number of the thin and vertically superimposed layers into controlsignals that control a stereolithography machine to create, layer bysuperimposed layer, the ophthalmic lens in a bath of aphotocurable/crosslinkable or polymerizable device-forming material.

The present invention, in a further aspect, provides a computer programproduct for use in a computer system to produce an ophthalmic lens bymeans of stereolithography, the computer program product comprising: arecording medium; means, recorded on the recording medium, for designinga 3-D mathematical model of the ophthalmic lens based on theprescription of an eye of a patient; means, recorded on the recordingmedium, for mathematically slicing the 3-D mathematical model into anumber of thin and vertically superimposed layers, each layer having adefined thickness profile and a geometry corresponding to a planar orcurved section of the 3-D mathematical model at the level of that layer;and means, recorded on the recording medium, for converting thethickness profile and the geometry of each of a number of the thin andvertically superimposed layers into control signals that control astereolithography machine to create, layer by superimposed layer, theophthalmic lens in a bath of a crosslinkable or polymerizabledevice-forming material.

While the invention has been described with reference to preferred andexample embodiments, it will be understood by those skilled in the artthat a variety of modifications, additions and deletions are within thescope of the invention, as defined by the following claims.

1. A method for manufacturing an ophthalmic device comprising:introducing a volume of photocurable material into a container; whereinsaid container comprises a mold surface; creating a digital 3-Dmathematical model defining corrective needs of an eye; and projectingprogrammed patterns of UV light through said mold via a patterngenerator; wherein said programmed patterns of UV light cure saidphotocurable material into an ophthalmic device shape defined by saidmold surface and said digital model.
 2. The method defined in claim 1,wherein said programmed patterns of UV light are determined by enteringsaid digital model into a software program.
 3. The method defined inclaim 1, wherein said mold surface is a single mold surface.
 4. Themethod defined in claim 3, wherein said single mold surface is a malemold surface.
 5. The method defined in claim 1, wherein said ophthalmicdevice shape is determined by duration and intensity of said patterns ofUV light.
 6. The method defined in claim 1, wherein said patterns of UVlight are projected individually.
 7. The method defined in claim 1,wherein said patterns of UV light are projected as a series.
 8. Themethod defined in claim 1, wherein said patterns of UV light areprojected with a gray scale, wherein said gray scale is defined bydegree of defocus of said UV light.
 9. The method defined in claim 1,wherein said digital model comprising a plurality of thin superimposedlayers each layer having a defined thickness profile and a geometrycorresponding to a planar or curved section of said digital 3-Dmathematical model.
 10. The method defined in claim 9, wherein saidthickness profiles and the geometry of each thin superimposed layer areconverted into control signals which control said pattern generator tocreate, layer by superimposed layer, said ophthalmic device from saidphotocurable material.
 11. A system for manufacturing an ophthalmicdevice, comprising: a computer system; means for communication with saidcomputer system for prompting a user to enter a prescription of an eye;means for designing a digital 3-D mathematical model of the ophthalmicdevice based on the prescription; means for digitally determining thedigital 3-D mathematical model comprising geometry corresponding to across-section of the digital 3-D mathematical model; means forconverting the geometry of the digital 3-D mathematical model intocontrol signals that control a stereolithography machine to create theophthalmic device onto a male mold immersed in a bath of photocurablematerial.
 12. A system of claim 11, wherein said means for communicationwith said computer system is a modem linked to a computer through theinternet.
 13. A system of claim 11, wherein said system furthercomprises a wavefront sensor which determines the wavefront aberrationsof an eye.
 14. A system of claim 13, wherein said system furthercomprises a corneal topographer or videokeratoscope which determinescorneal topographic data of the eye.
 15. A system of claim 11, whereinsaid system further comprises a stereolithography machine.
 16. A systemof claim 11, wherein said mold is a single male mold.